// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/memory/shared_memory.h"

#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>

#include <limits>

#include "base/logging.h"

namespace base {

SharedMemoryCreateOptions::SharedMemoryCreateOptions()
    : name_deprecated(nullptr)
    , open_existing_deprecated(false)
    , size(0)
    , executable(false)
    , share_read_only(false)
{
}

SharedMemory::SharedMemory()
    : mapped_file_(-1)
    , mapped_size_(0)
    , memory_(NULL)
    , read_only_(false)
    , requested_size_(0)
{
}

SharedMemory::SharedMemory(const SharedMemoryHandle& handle, bool read_only)
    : mapped_file_(handle.fd)
    , mapped_size_(0)
    , memory_(NULL)
    , read_only_(read_only)
    , requested_size_(0)
{
}

SharedMemory::~SharedMemory()
{
    Unmap();
    Close();
}

// static
bool SharedMemory::IsHandleValid(const SharedMemoryHandle& handle)
{
    return handle.fd >= 0;
}

// static
SharedMemoryHandle SharedMemory::NULLHandle()
{
    return SharedMemoryHandle();
}

// static
void SharedMemory::CloseHandle(const SharedMemoryHandle& handle)
{
    DCHECK_GE(handle.fd, 0);
    if (close(handle.fd) < 0)
        DPLOG(ERROR) << "close";
}

// static
SharedMemoryHandle SharedMemory::DuplicateHandle(
    const SharedMemoryHandle& handle)
{
    int duped_handle = HANDLE_EINTR(dup(handle.fd));
    if (duped_handle < 0)
        return base::SharedMemory::NULLHandle();
    return base::FileDescriptor(duped_handle, true);
}

bool SharedMemory::CreateAndMapAnonymous(size_t size)
{
    // Untrusted code can't create descriptors or handles.
    return false;
}

bool SharedMemory::Create(const SharedMemoryCreateOptions& options)
{
    // Untrusted code can't create descriptors or handles.
    return false;
}

bool SharedMemory::Delete(const std::string& name)
{
    return false;
}

bool SharedMemory::Open(const std::string& name, bool read_only)
{
    return false;
}

bool SharedMemory::MapAt(off_t offset, size_t bytes)
{
    if (mapped_file_ == -1)
        return false;

    if (bytes > static_cast<size_t>(std::numeric_limits<int>::max()))
        return false;

    if (memory_)
        return false;

    memory_ = mmap(NULL, bytes, PROT_READ | (read_only_ ? 0 : PROT_WRITE),
        MAP_SHARED, mapped_file_, offset);

    bool mmap_succeeded = memory_ != MAP_FAILED && memory_ != NULL;
    if (mmap_succeeded) {
        mapped_size_ = bytes;
        DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) & (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
    } else {
        memory_ = NULL;
    }

    return mmap_succeeded;
}

bool SharedMemory::Unmap()
{
    if (memory_ == NULL)
        return false;

    if (munmap(memory_, mapped_size_) < 0)
        DPLOG(ERROR) << "munmap";
    memory_ = NULL;
    mapped_size_ = 0;
    return true;
}

SharedMemoryHandle SharedMemory::handle() const
{
    return FileDescriptor(mapped_file_, false);
}

void SharedMemory::Close()
{
    if (mapped_file_ > 0) {
        if (close(mapped_file_) < 0)
            DPLOG(ERROR) << "close";
        mapped_file_ = -1;
    }
}

bool SharedMemory::ShareToProcessCommon(ProcessHandle process,
    SharedMemoryHandle* new_handle,
    bool close_self,
    ShareMode share_mode)
{
    if (share_mode == SHARE_READONLY) {
        // Untrusted code can't create descriptors or handles, which is needed to
        // drop permissions.
        return false;
    }
    const int new_fd = dup(mapped_file_);
    if (new_fd < 0) {
        DPLOG(ERROR) << "dup() failed.";
        return false;
    }

    new_handle->fd = new_fd;
    new_handle->auto_close = true;

    if (close_self) {
        Unmap();
        Close();
    }
    return true;
}

} // namespace base
